Crystalline substituted pyrazines as pgi2 receptor agonists

ABSTRACT

A main object of the present invention is to provide a novel crystal of 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}acetic acid (hereinafter referred to as “Compound B”). 
     A form-I crystal of Compound B, which shows peaks at diffraction angles (2θ) of 6.4°, 8.1°, 9.5°, 10.9°, 13.2°, 15.7°, 17.0°, 19.5°, 20.3°, 21.0°, and 22.8° in a powder X-ray diffraction spectrum obtained using a Cu-Kα radiation (λ=1.54 Å). 
     A form-II crystal of Compound B, which shows peaks at diffraction angles (2θ) of 9.6°, 11.4°, 11.7°, 16.3°, 17.5°, 18.5°, 18.7°, 19.9°, 20.1°, 21.0°, and 24.6° in a powder X-ray diffraction spectrum obtained using a Cu-Kα radiation (λ=1.54 Å).

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional of co-pending U.S. applicationSer. No. 16/650,390 having a § 371(c) filing date of Mar. 25, 2020,which is a U.S. national stage application under 35 U.S.C. § 371 ofInternational Patent Application No. PCT/JP2018/035828 filed on Sep. 27,2018, which claims the benefit of foreign priority to Japanese PatentApplication No. JP 2017-187296 filed on Sep. 28, 2017, the disclosuresof all of which are hereby incorporated by reference in theirentireties. The International Application was published in Japanese onApr. 4, 2019, as International Publication No. WO 2019/065792 A1 underPCT Article 21(2).

TECHNICAL FIELD

The present invention relates to a novel crystal of2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}acetic acid(hereinafter referred to as “Compound B”).

BACKGROUND ART

A pharmaceutical product is required to maintain its quality over a longperiod of time even under various conditions of distribution, storage,etc. Therefore, a compound to serve as an active ingredient is requiredto have high physicochemical stability. Due to this, as an activeingredient of a pharmaceutical product, a crystal which can be expectedto have high stability is generally adopted.

In a process for screening a crystal of an active ingredient of apharmaceutical product, not only is it difficult to find optimalconditions for obtaining the crystal, but also, even if the crystal isobtained, the existence of polymorphism is often problematic. Theproblem is caused because there is a difference in physicochemicalstability depending on the crystal form.

Further, if the crystal form to be adopted as an active ingredient of apharmaceutical product is erroneously selected, a decrease in purity,crystal form transformation, or the like occurs depending on theexternal environment during storage, and thus, it becomes difficult tomaintain the quality of the compound constant, and therefore, dependingon the crystal form, an unexpected event such as a decrease in drugefficacy or an adverse effect may be caused. Due to this, when a crystalof a compound to serve as an active ingredient of a pharmaceuticalproduct is acquired successfully, it is necessary to perform strictevaluation and examination of the physicochemical stability of thepolymorphism.

However, it is impossible to predict the existence or non-existence ofpolymorphism or a stable crystal form from the structure of a compound,and moreover, there exists a compound which cannot be crystallized insome cases, and it is necessary to variously study the conditions forforming a crystal for each compound.

On the other hand, Compound B is known to have an excellent PGI2receptor agonistic effect and show various medicinal effects such as aplatelet aggregation inhibitory effect, a vasodilating effect, abronchial smooth muscle dilating effect, a lipid deposition inhibitoryeffect, and a leukocyte activation inhibitory effect (see, for example,PTL 1 to PTL 6). However, the current situation is that it is not knownwhether or not a crystal can be formed, much less whether or notpolymorphism exists, and it is an important object to acquire an optimalcrystal for development thereof as a pharmaceutical product.

CITATION LIST Patent Literature

-   [PTL 1] WO 2002/088084-   [PTL 2] WO 2009/157396-   [PTL 3] WO 2009/107736-   [PTL 4] WO 2009/154246-   [PTL 5] WO 2009/157397-   [PTL 6] WO 2009/157398-   [PTL 7] US 2014/0221397-   [PTL 8] US 2011/0178103-   [PTL 9] US 2011/0015211-   [PTL 10] US 2011/0118254-   [PTL 11] US 2011/0105518

Non Patent Literature

-   [NPL 1] Hepatology, 2007, Vol. 45, No. 1, pp. 159-169-   [NPL 2] PubMed: Nihon Yakurigaku Zasshi, 2001, February, 117(2), pp.    123-130, Abstract-   [NPL 3] International Angiology, 29, Suppl. 1 to No. 2, pp. 49-54,    2010-   [NPL 4] Japanese Journal of Clinical Immunology, Vol. 16, No. 5, pp.    409-414, 1993-   [NPL 5] Japanese Journal of Thrombosis and Hemostasis, Vol. 1, No.    2, pp. 94-105, 1990, Abstract-   [NPL 6] The Journal of Rheumatology, Vol. 36, No. 10, pp. 2244-2249,    2009-   [NPL 7] The Japanese Journal of Pharmacology, Vol. 43, No. 1, pp.    81-90, 1987-   [NPL 8] British Heart Journal, Vol. 53, No. 2, pp. 173-179, 1985-   [NPL 9] The Lancet, 1, 4880, pt 1, pp. 569-572, 1981-   [NPL 10] European Journal of Pharmacology, 449, pp. 167-176, 2002-   [NPL 11] The Journal of Clinical Investigation, 117, pp. 464-72,    2007-   [NPL 12] American Journal of Physiology Lung Cellular and Molecular    Physiology, 296: L648-L656 2009

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide a crystal of Compound Bhaving excellent physicochemical stability and also to provide apharmaceutical composition containing the crystal as an activeingredient.

Solution to Problem

A method for producing Compound B is disclosed in Example 42 of PTL 1.However, in Example 42 of PTL 1, it is not specified what form ofCompound B was obtained.

Therefore, when the present inventor made an attempt to produce CompoundB according to the same procedure as the method disclosed in Example 42of PTL 1, it was found that the form is a crystal (hereinafter referredto as “form-III crystal”) (see the below-mentioned Reference Example 1).The results of powder X-ray diffraction measurement, IR measurement, andDSC measurement of the form-III crystal are shown in FIG. 1, FIG. 2, andFIG. 3, respectively.

However, as shown in the below-mentioned Test Example 1, it was foundthat the form-III crystal is thermodynamically unstable, and therefore,the present inventor made intensive studies in order to achieve theabove object, and as a result, it was found that there exist a form-Icrystal and a form-II crystal, each of which is thermodynamically morestable, and thus, the present invention was completed.

The present invention can include, for example, the following (1) to(7).

(1) A form-I crystal of Compound B (hereinafter referred to as “form-Icrystal of the present invention”), which shows diffraction peaks atdiffraction angles (2θ) of 6.4°, 8.1°, 9.5°, 10.9°, 13.2°, 15.7°, 17.0°,19.5°, 20.3°, 21.0°, and 22.8° in a powder X-ray diffraction spectrumobtained using a Cu-Kα radiation (λ=1.54 Å).

(2) A form-I crystal of the present invention, which shows absorptionpeaks at wavenumbers of 2874 cm⁻¹, 1736 cm⁻¹, 1558 cm⁻¹, 1375 cm⁻¹, 1126cm⁻¹, and 696 cm⁻¹ in an infrared absorption spectrum.

(3) A form-I crystal of the present invention, which has an endothermicpeak at 127° C. in differential scanning calorimetry.

(4) A form-II crystal of Compound B (hereinafter referred to as “form-IIcrystal of the present invention”), which shows diffraction peaks atdiffraction angles (2θ) of 9.6°, 11.4°, 11.7°, 16.3°, 17.5°, 18.5°,18.7°, 19.9°, 20.1°, 21.0°, and 24.6° in a powder X-ray diffractionspectrum obtained using a Cu-Kα radiation (λ=1.54 Å).

(5) A form-II crystal of the present invention, which shows absorptionpeaks at wavenumbers of 2867 cm⁻¹, 1749 cm⁻¹, 1568 cm⁻¹, 1382 cm⁻¹, 1131cm⁻¹, and 701 cm⁻¹ in an infrared absorption spectrum.

(6) A form-II crystal of the present invention, which has an endothermicpeak at 147° C. in differential scanning calorimetry.

(7) A pharmaceutical composition containing the crystal according to anyone of (1) to (6) as an active ingredient (hereinafter referred to as“pharmaceutical composition of the present invention”).

When specifying a diffraction angle (20) for a diffraction peak inExamples and the claims of the present invention, it should beunderstood that an obtained value is within the range of the value±0.2°, preferably within the range of the value ±0.1°.

Further, when specifying an absorption peak in an infrared absorptionspectrum (hereinafter referred to as “IR spectrum”) in Examples and theclaims of the present invention, it should be understood that anobtained value is within the range of the value ±2 cm⁻¹, preferablywithin the range of the value ±1 cm⁻¹.

Further, when specifying an endothermic peak by a differential scanningcalorimetry (hereinafter referred to as “DSC”) in Examples and theclaims of the present invention, it should be understood that anobtained value is within the range of the value ±3° C., preferablywithin the range of the value ±2° C.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a powder X-ray diffraction spectrum chart of a form-IIIcrystal. The vertical axis represents a peak intensity (cps) and thehorizontal axis represents a diffraction angle (2θ [°]).

FIG. 2 shows an IR spectrum chart of the form-III crystal. The verticalaxis represents a transmittance (%) and the horizontal axis represents awavenumber (cm⁻¹).

FIG. 3 shows a DSC measurement chart when the temperature of theform-III crystal was increased by 10° C. per minute. The vertical axisin the drawing represents an exothermic amount (mW) (in the case of anegative value, the value represents an endothermic amount) and thehorizontal axis represents a temperature (° C.).

FIG. 4 shows a powder X-ray diffraction spectrum chart of the form-Icrystal of the present invention. The vertical axis represents a peakintensity (cps) and the horizontal axis represents a diffraction angle(2θ [°]).

FIG. 5 shows a powder X-ray diffraction spectrum chart of the form-IIcrystal of the present invention. The vertical axis represents a peakintensity (cps) and the horizontal axis represents a diffraction angle(2θ [°]).

FIG. 6 shows an IR spectrum chart of the form-I crystal of the presentinvention. The vertical axis represents a transmittance (%) and thehorizontal axis represents a wavenumber (cm⁻¹).

FIG. 7 shows an IR spectrum chart of the form-II crystal of the presentinvention. The vertical axis represents a transmittance (%) and thehorizontal axis represents a wavenumber (cm⁻¹).

FIG. 8 shows a DSC measurement chart when the temperature of the form-Icrystal of the present invention was increased by 10° C. per minute. Thevertical axis represents an exothermic amount (mW) per second (in thecase of a negative value, the value represents an endothermic amount)and the horizontal axis represents a temperature (° C.).

FIG. 9 shows a DSC measurement chart when the temperature of the form-IIcrystal of the present invention was increased by 10° C. per minute. Thevertical axis in the drawing represents an exothermic amount (mW) (inthe case of a negative value, the value represents an endothermicamount) and the horizontal axis represents a temperature (° C.).

DESCRIPTION OF EMBODIMENTS A. Form-I Crystal of the Present Invention

The form-I crystal of the present invention is characterized in that itshows diffraction peaks at diffraction angles (2θ) of 6.4°, 8.1°, 9.5°,10.9°, 13.2°, 15.7°, 17.0°, 19.5°, 20.3°, 21.0°, and 22.8° in a powderX-ray diffraction spectrum obtained using a Cu-Kα radiation (λ=1.54 Å).Further, it is preferably characterized in that it shows diffractionpeaks at 15.8°, 17.2°, 21.9°, 23.7°, 24.5°, 25.5°, 25.8°, 28.9°, and32.0° in addition to the above-mentioned diffraction peaks.

Further, the form-I crystal of the present invention is characterized inthat it shows absorption peaks at wavenumbers of 2874 cm⁻¹, 1736 cm⁻¹,1558 cm⁻¹, 1375 cm⁻¹, 1126 cm⁻¹, and 696 cm⁻¹ in an IR spectrum (KBrmethod).

Further, the form-I crystal of the present invention is characterized inthat it has an endothermic peak at 127° C. in differential scanningcalorimetry.

The form-I crystal of the present invention can be obtained by, forexample, the method described in the below-mentioned Example 1.

B. Form-II Crystal of the Present Invention

The form-II crystal of the present invention is characterized in that itshows diffraction peaks at diffraction angles (2θ) of 9.6°, 11.4°,11.7°, 16.3°, 17.5°, 18.5°, 18.7°, 19.9°, 20.1°, 21.0°, and 24.6° in apowder X-ray diffraction spectrum obtained using a Cu-Kα radiation(λ=1.54 Å). Further, it is preferably characterized in that it showsdiffraction peaks at 19.4°, 20.6°, 21.1°, 21.7°, 22.7°, 26.6°, 26.7°,28.8°, and 30.8° in addition to the above-mentioned diffraction peaks.

Further, the form-II crystal of the present invention is characterizedin that it shows absorption peaks at wavenumbers of 2867 cm⁻¹, 1749cm⁻¹, 1568 cm⁻¹, 1382 cm⁻¹, 1131 cm⁻¹, and 701 cm⁻¹ in an IR spectrum(KBr method).

Further, the form-II crystal of the present invention is characterizedin that it has an endothermic peak at 147° C. in differential scanningcalorimetry.

The form-II crystal of the present invention can be obtained by, forexample, the method described in the below-mentioned Example 2.

C. Medical Application⋅Pharmaceutical Composition of the PresentInvention

The Compound B according to the present invention has an excellent PGI2receptor agonistic effect and shows various medicinal effects such as aplatelet aggregation inhibitory effect, a vasodilating effect, abronchial smooth muscle dilating effect, a lipid deposition inhibitoryeffect, and a leukocyte activation inhibitory effect (see, for example,PTL 1).

Therefore, the form-I crystal of the present invention, the form-IIcrystal of the present invention (hereinafter, collectively referred toas “crystal of the present invention”), or the pharmaceuticalcomposition of the present invention is useful as a preventive agent ora therapeutic agent for transient ischemic attack (TIA), diabeticneuropathy (see, for example, NPL 1), diabetic gangrene (see, forexample, NPL 1), a peripheral circulatory disturbance [for example,chronic arterial occlusion (see, for example, NPL 2), intermittentclaudication (see, for example, NPL 3), peripheral embolism, vibrationsyndrome, or Raynaud's disease] (see, for example, NPL 4 and NPL 5), aconnective tissue disease [for example, systemic lupus erythematosus,scleroderma (see, for example, PTL 7 and NPL 6), a mixed connectivetissue disease, or a vasculitic syndrome], reocclusion/restenosis afterpercutaneous transluminal coronary angioplasty (PTCA), arteriosclerosis,thrombosis (for example, acute-phase cerebral thrombosis or pulmonaryembolism) (see, for example, NPL 5 and NPL 7), hypertension, pulmonaryhypertension, an ischemic disease [for example, cerebral infarction ormyocardial infarction (see, for example, NPL 8)], angina pectoris (forexample, stable angina pectoris or unstable angina pectoris) (see, forexample, NPL 9), glomerulonephritis (see, for example, NPL 10), diabeticnephropathy (see, for example, NPL 1), chronic renal failure (see, forexample, PTL 8), allergy, bronchial asthma (see, for example, NPL 11),ulcer, pressure ulcer (bedsore), restenosis after coronary interventionsuch as atherectomy or stent implantation, thrombocytopenia by dialysis,a disease in which fibrogenesis in an organ or a tissue is involved [forexample, a renal disease {for example, tubulointerstitial nephritis(see, for example, PTL 9)}, a respiratory disease {for example,interstitial pneumonia (for example, pulmonary fibrosis) (see, forexample, PTL 9), a chronic obstructive pulmonary disease (see, forexample, NPL 12)}, a digestive disease (for example, hepatocirrhosis,viral hepatitis, chronic pancreatitis, or scirrhous gastric cancer), acardiovascular disease (for example, myocardial fibrosis), a bone orarticular disease (for example, bone marrow fibrosis or rheumatoidarthritis), a skin disease (for example, postoperative cicatrix, burncicatrix, keloid, or hypertrophic cicatrix), an obstetric disease (forexample, uterine fibroid), a urinary disease (for example, prostatichypertrophy), other diseases (for example, Alzheimer's disease,sclerosing peritonitis, type I diabetes, and postoperative organadhesion)], erectile dysfunction (for example, diabetic erectiledysfunction, psychogenic erectile dysfunction, psychotic erectiledysfunction, erectile dysfunction due to chronic renal failure, erectiledysfunction after pelvic operation for resection of the prostate, orvascular erectile dysfunction associated with aging orarteriosclerosis), an inflammatory bowel disease (for example,ulcerative colitis, Crohn's disease, intestinal tuberculosis, ischemiccolitis, or intestinal ulcer associated with Behcet disease) (see, forexample, PTL 10), gastritis, gastric ulcer, an ischemic eye disease (forexample, retinal artery occlusion, retinal vein occlusion, or ischemicoptic neuropathy), sudden hearing loss, avascular necrosis of bone, anintestinal damage caused by administration of a non-steroidalanti-inflammatory agent (NSAID) (for example, diclofenac, meloxicam,oxaprozin, nabumetone, indomethacin, ibuprofen, ketoprofen, naproxen, orcelecoxib) (there is no particular limitation as long as it is a damageoccurring in, for example, the duodenum, small intestine, or largeintestine, however, for example, a mucosal damage such as erosion orulcer occurring in the duodenum, small intestine, or large intestine),or symptoms (for example, paralysis, dullness in sensory perception,pain, numbness, or a decrease in walking ability) associated with spinalcanal stenosis (for example, cervical spinal canal stenosis, thoracicspinal canal stenosis, lumbar spinal canal stenosis, coexisting cervicaland lumbar spinal stenosis, or sacral spinal stenosis) (see PTL 11).

In addition, the crystal of the present invention or the pharmaceuticalcomposition of the present invention is also useful as an acceleratingagent for gene therapy or angiogenic therapy such as autologous bonemarrow transplantation, or an accelerating agent for angiogenesis inrestoration of peripheral artery or angiogenic therapy.

When the crystal of the present invention is administered as apharmaceutical, the crystal is administered as it is, or is contained ina pharmaceutically acceptable nontoxic inert carrier in an amount withinthe range of, for example, 0.1% to 99.5%, preferably within the range of0.5% to 90%.

Examples of the carrier include solid, semi-solid, or liquid diluents,fillers, and other auxiliary agents for pharmaceutical formulation.Among these, one type or two or more types can be used.

The pharmaceutical composition of the present invention may be in anyform of preparations for oral administration such as a powder, acapsule, a tablet, a sugar-coated tablet, a granule, a powderpreparation, a suspension, a liquid, a syrup, an elixir, and a troche,and parenteral preparations such as an injection and a suppository in asolid or liquid dosage unit. It may be in the form of a sustainedrelease preparation. Among these, particularly, preparations for oraladministration such as a tablet are preferred.

The powder can be produced by grinding the crystal of the presentinvention to an appropriate fineness.

The powder preparation can be produced by grinding the crystal of thepresent invention to an appropriate fineness, and then mixing the groundcrystal with a similarly ground pharmaceutical carrier, for example, anedible carbohydrate such as starch or mannitol. A flavor, apreservative, a dispersant, a colorant, a perfume, or the like can bearbitrarily added thereto.

The capsule can be produced by firstly filling a powder or a powderpreparation formed into a powdery shape as described above or agranulated material as will be described in the section on the tabletin, for example, a capsule shell such as a gelatin capsule. Further, thecapsule can be produced by mixing a lubricant or a fluidizing agent suchas colloidal silica, talc, magnesium stearate, calcium stearate, orsolid polyethylene glycol with a powder or a powder preparation formedinto a powdery shape, and thereafter performing a filling operation. Itis possible to improve the effectiveness of the pharmaceutical when thecapsule is taken if a disintegrating agent or a solubilizing agent suchas carboxymethyl cellulose, carboxymethyl cellulose calcium,low-substituted hydroxypropyl cellulose, croscarmellose sodium,carboxymethyl starch sodium, calcium carbonate, or sodium carbonate isadded thereto.

Further, it is also possible to form a soft capsule by suspending anddispersing the fine powder of the crystal of the present invention in avegetable oil, polyethylene glycol, glycerin, or a surfactant, andwrapping the resulting material with a gelatin sheet.

The tablet can be produced by adding an excipient to the powderedcrystal of the present invention to prepare a powder mixture,granulating or slagging the powder mixture, and then adding adisintegrating agent or a lubricant thereto, followed by tableting.

The powder mixture can be prepared by mixing the suitably powderedcrystal of the present invention with a diluent or a base. If necessary,it is possible to add a binder (for example, carboxymethyl cellulosesodium, methyl cellulose, hydroxypropylmethyl cellulose, gelatin,polyvinylpyrrolidone, or polyvinyl alcohol), a dissolution retardingagent (for example, paraffin), a reabsorbing agent (for example, aquaternary salt), an adsorbent (for example, bentonite or kaolin), orthe like thereto.

The granule can be produced by firstly wetting the powder mixture with abinder, for example, a syrup, a starch paste, gum Arabic, a cellulosesolution, or a polymeric substance solution, stirring and mixing the wetmixture, and then, drying and crushing the mixture. In place of thegranulation of the powder in this manner, it is also possible to formthe granule by firstly subjecting the powder to a tableting machine, andthereafter crushing the slag as obtained in an incomplete shape. Byadding stearic acid, a stearate salt, talc, a mineral oil, or the likeas a lubricant to the thus produced granule, the granules can beprevented from adhering to each other.

Further, the tablet can also be produced by mixing the crystal of thepresent invention with a fluid inert carrier, and thereafter directlytableting the resulting mixture without undergoing a granulation orslagging step as described above.

The thus produced tablet can be subjected to film coating or sugarcoating. It is also possible to use a transparent or semi-transparentprotective coating film made of a shellac sealing coating film, acoating film made of a sugar or a polymeric material, or a polishedcoating film made of a wax.

Another preparation for oral administration, for example, a liquid, asyrup, a troche, or an elixir can also be formulated into a dosage unitform such that a predetermined amount thereof contains a predeterminedamount of the crystal of the present invention.

The syrup can be produced by dissolving the crystal of the presentinvention in an appropriate aqueous flavor solution. The elixir can beproduced using a non-toxic alcohol carrier.

The suspension can be produced by dispersing the crystal of the presentinvention in a non-toxic carrier. If necessary, it is possible to add asolubilizing agent or an emulsifier (for example, an ethoxylatedisostearyl alcohol or a polyoxyethylene sorbitol ester), a preservative,a flavor-imparting agent (for example, peppermint oil or saccharine), orthe like thereto.

If necessary, the dosage unit formulation for oral administration may bemicroencapsulated. It is also possible to extend the duration of actionor achieve sustained release by coating the formulation or embedding theformulation in a polymer, a wax, or the like.

The preparation for parenteral administration may be in a liquid dosageunit form for subcutaneous, intramuscular or intravenous injection, forexample, in the form of a solution or a suspension. The preparation forparenteral administration can be produced by suspending or dissolving apredetermined amount of the crystal of the present invention in anon-toxic liquid carrier meeting the purpose of injection, for example,an aqueous or oily medium, and then sterilizing the suspension orsolution. It is also possible to add a stabilizing agent, apreservative, an emulsifier, or the like thereto.

The suppository can be produced by dissolving or suspending the crystalof the present invention in a solid which has a low melting point and issoluble or insoluble in water, for example, polyethylene glycol, cacaobutter, a semi-synthetic oil or fat [for example, Witepsol (registeredtrade mark)], a higher ester (for example, myristyl palmitate ester), ora mixture thereof.

The dose varies depending on the state of a patient such as body weightor age, the administration route, the nature and severity of a disease,or the like, however, the dose as the amount of the crystal of thepresent invention per day per adult is suitably within the range of0.001 mg to 100 mg, preferably within the range of 0.01 mg to 10 mg.

In some cases, a dose not more than the above range may be sufficient,or on the other hand, a dose not less than the above range may beneeded. Further, the preparation can be administered once to severaltimes a day or can be administered with an interval of one to severaldays.

EXAMPLES

Hereinafter, the present invention will be described in more detail withreference to Examples and Test Examples, however, the present inventionis by no means limited thereto.

A powder X-ray diffraction spectrum was measured using SmartLab(manufactured by Rigaku Corporation) (optical system: focusing method,voltage: 45 kV, current: 200 mA, wavelength: Cu-Kα, solar slit: 5.0°,scan range: 4 to 40°, scan speed: 47.3°/min, sample rotation: 60°/min).

An IR spectrum was measured using IR Affinity-1 (manufactured byShimadzu Corporation) (measurement mode: % Transmittance, cumulativenumber: 16 times, resolution: 2.0, wavenumber range: 400 to 4000 cm⁻¹).

A DSC was measured using DSC-50 (manufactured by Shimadzu Corporation)(cell: alumina (open), gas: nitrogen (20.0 mL/min), heating rate: 10°C./min, holding temperature: 250° C., holding time: 0 min).

Reference Example 1: Production of form-III Crystal

After tert-butyl2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}acetate(see, for example, PTL 1) (13.15 g) was dissolved in methanol (179.7mL), a 1 N aqueous sodium hydroxide solution (41.47 mL) was addedthereto. After the resulting mixture was heated under reflux for 1 hour,the solvent was distilled off under reduced pressure, and water wasadded to the residue to dissolve the residue. After washing wasperformed with diethyl ether, the obtained aqueous layer was neutralizedwith 1 N hydrochloric acid (44 mL), and extraction was performed withethyl acetate. The obtained ethyl acetate layer was dried over anhydrousmagnesium sulfate, and the solvent was distilled off under reducedpressure, and then, diisopropyl ether was added to the residue to effectcrystallization. The resulting crystal was filtered and washed with anappropriate amount of diisopropyl ether. The crystal was dried at 40° C.under reduced pressure, whereby a form-III crystal (9.88 g) wasobtained.

The results of powder X-ray diffraction measurement, IR measurement, andDSC measurement of the form-III crystal are shown in FIG. 1, FIG. 2, andFIG. 3, respectively.

diffraction angles (2θ): 8.4°, 12.6°, 13.4°, 14.3°, 14.6°, 15.9°, 16.9°,18.0°, 18.8°, 19.4°, 20.3°, 20.6°, 21.6°, 21.7°, 22.3°, 22.5°, 23.3°,23.7°, 23.9°, 27.0°, 29.6°, and 30.8°

IR absorption peaks: 2867 cm⁻¹, 1747 cm⁻¹, 1558 cm⁻¹, 1380 cm⁻¹, 1131cm⁻¹, and 701 cm⁻¹

DSC endothermic peak: 118° C.

Reference Example 2: Production of Compound B

To a suspension of2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl)acetamide(see, for example, PTL 1) (300 g) in isopropyl alcohol (1425 mL), anaqueous sodium hydroxide solution (a solution obtained by dissolvingsodium hydroxide (120.8 g) in water (570 mL)) was added. After stirringwas performed at 100° C. for 11 hours, the resulting mixture was cooledto 10° C. or lower. After concentrated hydrochloric acid was addeddropwise thereto, stirring was performed at 10° C. or lower for 1 hour,the resulting precipitate was filtered and washed with an appropriateamount of a 50% aqueous isopropyl alcohol solution, water, andacetonitrile. The precipitate was dried at 65° C. under reducedpressure, whereby a target compound (208.3 g) was obtained.

Example 1: Production of form-I Crystal of the Present Invention

Compound B (63 g) produced in Reference Example 2 was dissolved inacetonitrile (315 mL) at 90° C., and stirring was performed at the sametemperature for 30 minutes. The solution was filtered, and washing wasperformed with 5 mL of acetonitrile, and stirring with heating wasperformed again. As stimulation, a small amount of Compound B producedin Reference Example 2 was added thereto, followed by gradual cooling,and stirring was performed at 10° C. or lower for 1 hour, and then, thecrystal was filtered and washed with an appropriate amount ofacetonitrile. The crystal was dried at 65° C. under reduced pressure,whereby the form-I crystal of the present invention (59.5 g) wasobtained.

The results of powder X-ray diffraction measurement, IR measurement, andDSC measurement of the form-I crystal of the present invention are shownin FIG. 4, FIG. 6, and FIG. 8, respectively.

diffraction angles (2θ): 6.4°, 8.1°, 9.5°, 10.9°, 13.2°, 15.7°, 15.8°,17.0°, 17.2°, 19.5°, 20.3°, 21.0°, 21.9°, 22.8°, 23.7°, 24.5°, 25.5°,25.8°, 28.9°, and 32.0°

IR absorption peaks: 2874 cm⁻¹, 1736 cm⁻¹, 1558 cm⁻¹, 1375 cm⁻¹, 1126cm⁻¹, and 696 cm⁻¹

DSC endothermic peak: 127° C.

Example 2: Production of form-II Crystal of the Present Invention

Compound B (0.5 g) produced in Reference Example 2 was dissolved inisopropyl alcohol (2.5 mL) and an 8% aqueous sodium hydroxide solution(1.5 mL) at 80° C., and stirring was performed at the same temperaturefor 30 minutes. The solution was gradually cooled to room temperature,and the pH of the solution was adjusted to 5 to 6 with a 4 N aqueoushydrochloric acid solution at room temperature, and then, stirring wasperformed at 10° C. or lower for 1 hour. Thereafter, the crystal wasfiltered and washed with an appropriate amount of water. The crystal wasdried at 65° C. under reduced pressure, whereby the form-II crystal ofthe present invention (0.45 g) was obtained.

The results of powder X-ray diffraction measurement, IR measurement, andDSC measurement of the form-II crystal of the present invention areshown in FIG. 5, FIG. 7, and FIG. 9, respectively.

diffraction angles (2θ): 9.6°, 11.4°, 11.7°, 16.3°, 17.5°, 18.5°, 18.7°,19.4°, 19.9°, 20.1°, 20.6°, 21.0°, 21.1°, 21.7°, 22.7°, 24.6°, 26.6°,26.7°, 28.8°, and 30.8°

IR absorption peaks: 2867 cm⁻¹, 1749 cm⁻¹, 1568 cm⁻¹, 1382 cm⁻¹, 1131cm⁻¹, and 701 cm⁻¹

DSC endothermic peak: 147° C.

Test Example 1: Stability Test

Different crystal forms of Compound B were placed in glass bottles,respectively, and the glass bottles were hermetically sealed and storedat 90° C. Samples were taken out after 1 day, 5 days, and 14 days, anddissolved in methanol at a concentration of 1 mg/mL to determine relatedsubstances by HPLC. With respect to the crystals after 14 days, thecrystal form was checked. The results are shown in Table 1.

TABLE 1 Form-I Form-II Form-III HPLC HPLC HPLC area area area Storageconditions Appearance (%) Appearance (%) Appearance (%) Before storageWhite crystal 99.8 Yellow crystal 100 Yellow crystal 99.9 90° C., after1 day No change 99.8 No change 100 No change 99.9 90° C., after 5 daysNo change 99.8 No change 100 No change 99.9 90° C., after 14 days Nochange 99.6 No change 99.9 No change 99.7 Crystal form after 14 daysForm-I + Form-II Form-II Form-II

From the above results, it was revealed that in any of the crystalforms, chemical stability is very high, however, the form-I and theform-III are gradually transformed into the form-II which isthermodynamically stable.

Test Example 2: Solvent Suspending Test of Form-I Crystal of the PresentInvention in Different Solvents

The form-I crystal of the present invention was mixed with differentsolvents, and stirring was performed at room temperature for 30 minutes.The formed crystals were obtained by filtration, and the crystal formswere determined. The results are shown in Table 2.

TABLE 2 Crystal form after 30 Solvent minutes at room temperaturecyclohexane Form-I + Form-II (1:1)  water Form-I + Form-II (10:1)2-propanol Form-I + Form-II (1:10) toluene Form-I + Form-II (10:1)

As described above, the form-I crystal of the present invention waspartially transformed into the form-II crystal of the present inventionwhen suspended in all the solvents. From these results, it was revealedthat the form-II crystal of the present invention is thermodynamicallystable when suspended in various solvents at room temperature.

1. A form-I crystal of2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}aceticacid, which shows diffraction peaks at diffraction angles (2θ) of 6.4°,8.1°, 9.5°, 10.9°, 13.2°, 15.7°, 17.0°, 19.5°, 20.3°, 21.0°, and 22.8°in a powder X-ray diffraction spectrum obtained using a Cu-Kα radiation(λ=1.54 Å).
 2. The form-I crystal of2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}acetic acidaccording to claim 1, which shows absorption peaks at wavenumbers of2874 cm⁻¹, 1736 cm⁻¹, 1558 cm⁻¹, 1375 cm⁻¹, 1126 cm⁻¹, and 696 cm⁻¹ inan infrared absorption spectrum.
 3. The form-I crystal of2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}acetic acidaccording to claim 1, which has an endothermic peak at 127° C. indifferential scanning calorimetry. 4-9. (canceled)